Coloring can be applied to the surface of contact lenses to alter the coloring of the eyes of the person wearing the lenses. The coloring of the pupil of the human eye is, however, very complex. The center of the pupil has a deep, almost black, solid color, while the outer periphery of the pupil has a lighter, distinguishable color such as brown, hazel, blue, green, or some blend thereof, although this outer periphery of the pupil is not uniform in color. The coloring may be deeper near the outer edges of the pupil than near the dark center, and the coloring may be a composition with a background of one color and fine lines which extend radially inward from the outer circumference of the pupil with the fine lines having a deeper, perhaps different color than the background color. A combination of three or four colors, therefore, may be required to duplicate the coloring of the human eye. Coloring printed on a contact lenses which, when fitted into the eyes of a wearer, will change the coloring of the eyes of the wearer and not appear to be unnatural, must have a pattern of colors which duplicates the pattern of the human eye.
To print a pattern having a plurality of colors onto a contact lens, the pattern must be broken down into sub patterns, with each sub pattern corresponding to one of the colors which make up the coloring of the pattern. The sub patterns must be aligned such that the printing ink of one color does not overlay upon the printing of ink of another color because the multiple layering of the ink will create an uneven surface which can cause irritation in the eye of the wearer, and it will give an unnatural coloring to the pattern. Both of these consequences reduce the desirability of the contact lens to which the coloring has been applied.
Machines are currently available which apply a plurality of sub patterns of color to a contact lens which combine into a single pattern by providing a carousel having a plurality of retainers for retaining lens to which colors are to be applied. As the carousel rotates the lens retained on a retainer is moved from one coloring station to another with the pattern for a different coloring applied at each of the stations. Each of the stations includes a vertically moveable print pad and a first assembly for applying a sub pattern of fresh ink to the print pad before the print pad is pressed against a contact lens and a second assembly for removing residue ink from the print pad after the pad has been used to apply ink to a contact lens. Each first assembly has an image die having a pattern therein which is moveable, or xe2x80x9cdoctored,xe2x80x9d to a first position at which ink is applied into the pattern of the die after which it is doctored to a second position below a print pad. The print pad is lowered and compressed upon the image die and thereafter elevated, after which the ink from the image die is retained on the print pad. The image die is doctored back to the first position at which ink is reapplied. With the image die doctored out from under the print pad, the carousal can be rotated to move the lens retainer with a contact lens thereon beneath the print pad, and the print pad is again lowered to apply ink to the surface of the contact lens. After the print pad is again raised, an incremental rotation of the carousal will then move the retainer and contact with printed material thereon towards its next stage.
Residue ink on the print pad is removed by a cleaning element in the form of a section of a three inch wide cellophane tape. When the print pad is lowered to the adhesive material, the tape adheres to any remaining ink left on the print pad. When the print pad is subsequently raised the role of cellophane tape is incrementally advanced to position a clean section of tape on the table for cleaning the print pad after the next printing cycle. The cycle is then repeated with the print pad moving downwardly for a brief period of time, first to receive ink from the image die, second to apply the ink to a contact lens, and third to contact the adhesive of the tape to remove excess ink from the surface thereof.
Machines as described above will produce high quality colored lenses with patterns printed thereon which duplicate the appearance of the pupil of the human eye, although such machines do have limitations. First, there are practical limitations to the size of the carousel and therefore there are limitations to the number of lenses which can be simultaneously printed by such machines. Second, by the nature of their circular configuration, the machines have substantial space requirements. Third, the machine moves one of the three elements of image die, cleaning table, and contact lens container successively below the print pad and the speed at which the machine operates is limited by the speed at which the elements can be successively first moved under the print pad and then be removed therefrom.
Another problem arises from the inks applied to objects such as contact lenses because each ink color has different properties for application and drying. Specifically different colored inks for contact lenses have different dwell times, the dwell time being the time fresh ink must set on the print pad before the ink is applied by the pad to the print surface. If ink is applied prematurely, it may blot and if the ink is retained on the print pad too long, it may continue to adhere to the pad and not be applied to the print surface. To retain an ink of a color on a print pad for a given period of time, the print pad can be held motionless over a print surface for a time period (the dwell time) which when added to the time required for the pad to be moved from the inking step to the printing step equals the given period of time. The dwell time for a carousel type machine cannot be individually adjusted without slowing the entire machine to accommodate the longest dwell time.
Another limiting factor to existing machines is the time needed for the ink to dry on a surface before the surface can receive the application of a different color ink. Existing machines must be operated at a sufficiently slow speed to allow a first application of ink to dry before a second is applied.
It would be desirable to provide a machine for which the dwell time for each print cycle can be individually adjusted. It would also be desirable to provide a means for accelerating the drying process for the ink.
Briefly, the present invention is embodied in a machine for applying a plurality of inked patterns, each with a different color, to a surface such as a contact lens to give the surface a desired appearance such as that of the pupil of a human eye. In accordance with the invention, the machine has a plurality of print stations in side-by-side relationship and a carriage is linearly moveable from one station to another. Where four colors are to be applied to a contact lens, the carriage would move across four color stations to thereby apply four colors to the lens, and where fewer colors are required, the carriage would be adapted to move to only the number of stations necessary to provide the required coloring. Each of the stations have a moveable image die having a planar horizontal surface with a pattern of indentations are for receiving a coloring material such as an ink. The image die is horizontally moveable for doctoring between a first position at which color is applied into the pattern of the die and a second position in which it can be contacted by a print pad for transferring the ink thereto.
Mounted on the carriage is a retainer for retaining the contact lens and a cleaning table across which segments of tape are incrementally advanced. Also mounted on the carriage is a gantry for retaining a horizontally and vertically moveable print pad, the horizontal movement being in a second direction perpendicular to the first direction of movement of the carriage. When the carriage is positioned at a given print station, movement of the print pad in the second direction will successively move the print pad over the image die of the given print station, the retainer on which the contact lens is retained, and the cleaning table across which the tape is advanced.
The movement of the carriage and the print pad are controlled by an appropriate motor, such as pneumatic cylinders. A first motor is provided to move the carriage from a first print station to a second print station, a second motor is provided to move the image die from its first position to a second position. A third motor moves the print pad to any one of three locations, the first location in which the print pad is over the cleaning table, the second location in which the print pad is over the image die, and the third location where the print pad is over the retainer for the contact lens. A fourth motor moves the print pad from an elevated position to a downward position to thereby apply the print pad successively against the image die, the print surface on the retainer, and the cleaning tape on the table.
Since the print pad is moveable on the carriage, the pad is repositioned for printing a new ink color by a single movement of the carriage to the next print station. Also, since all the steps of the printing process are linearly aligned in the second direction, a simple movement of the print pad along the gantry repositions the print pad to carry out each of the successive steps. Existing machines, on the other hand require two or more steps between successive operations of the print pad. One step to remove the completed operation from under the print pad, and a second step to move the next operation under the print pad. The speed at which existing machines can operate is limited by the multiplicity of steps required between successive operations of the print pad.
In accordance with one feature of the invention, a timer is provided at each print station to control the dwell time of the print pad following the inking of the print pad at the second location and prior to the application of the ink to the print surface.
Another feature of the invention is a blower to expedite the drying of the ink. According to this feature, air from a compressor is passed through a filter to remove small particles suspended therein, after which the stream of air from the compressor is directed to the print surface to facilitate the drying of ink applied thereto.